Cases of elevated deep moist convection initiation above frontal surfaces in 2015
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Abstract
Frontal structures, their associated parcel trajectories, and mesoscale circulations were analyzed to determine how they contributed to cases of elevated convection initiation (ECI). The steepest observed front had a mean slope of 1:130, while the shallowest front had a mean slope of 1:320, although frontal slopes were non-uniform. Isentropic ascent of the low-level jet (LLJ) on warm and stationary fronts was found to transport water vapour up the frontal surface, helping to reduce convective inhibition. When the LLJ ascended fronts it also caused upward vertical motion with maximum observed isentropic vertical velocities of -10 μb/s and maximum observed kinematic vertical velocities of -12 μb/s. The convergence of the LLJ was also shown to cause frontogenesis and the development/enhancement of potential vorticity (PV) anomalies. Both frontogenesis and PV anomalies were found to contribute to ECI.